So I've been trouble shooting this hard-shifting problem for a while now. I finally bought a vac. pump about a month or so ago and have come to the conclusion that my Modulator should be replace since it isn't holding a vacuum.

I have replaced the clear vacuum line and the rubber hose on the modulator itself and it still doesn't hold a vacuum. I ordered a new modulator, the pin and the rubber cap the other day and hopefully they will be here by the weekend.

While I was under the car last week I realized that the modulator might be a little harder to remove than I had anticipated. Any tips to get the thing off? Thanks...

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1985 Mercedes 300DT

It's been a while since I did this but IIRC, you remove the bolts on the clamp and then pry gently straight out (a couple of screwdrivers, one on each side) Be sure not to rock it too far to one side as you run the risk of breaking off the plastic pin that is behind (inside) the modulator. If the pin breaks, you may be able to retrieve it with forceps, if your lucky, or worst case.....removal of the valve body. Slow and easy.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Veg head ---- It's not too often that I get to offer advice on this column -- most folks here are way ahead of me. But I do have some experience on this one. When I tried to change the modulator on my 300D (bio also) I found access to be challenging. To make matters worse, I twisted too hard on the hex head screw (one of two) and stripped the head. Big problem. I considered lowering the transmission a bit for better access but was advised that this would not work. I eventually used a hole saw to cut a 2 3/4" access hole in my tunnell, allowing me access from the driver's compartment. Still had quite a time extracting the stripped bolt, but eventually got it. This might be pretty drastic for the purists out there, but it worked and the opening is all sealed up nicely (but can be reopened if I ever need access again).

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John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

is it bolted in? would make sense; i guess i was under the impression that is was just stuck in there...i didn't notice any bolts the other day...any idea what size bolts i should be looking for?

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1985 Mercedes 300DT

The 123 may be a little different on clearance, but I was able to remove the tranny mount and get enough room to work. But then again, I didn't have a stripped bolt to contend with.

The bolts hold a plate that surrounds the modulator.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Best I can recall it used a 5mm hex wrench. Mighty tight in there. I ultimately cut my allen wrench off and used it in a socket.

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John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

Meant 6 mm. I think the diagram I was using called it a 5mm but I think it really was a 6

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John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln

Do You Know That The Rubber Cover That Seals The Opening For The Mod Adj Has To Hold Vac Or You Will Think The Modulator Is Bad.
Larry Perkins Lou Ky

thanks,,,i ordered that as well...before i change the modulator i'll replace the cap first...

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1985 Mercedes 300DT